In a known game program, a radar function is used to discover enemy characters which are defined as opponents in the game application program. For example, JP H10-263205-A discloses a game device in which a video image showing a soccer game as seen from a viewpoint defined within a virtual space is displayed at the center of a screen and a small-sized radar screen is displayed independently of this background screen. In this game device, the viewpoint moves from the rear side of a player character which advances toward a ball, and the video image centered around this viewpoint is displayed on the entire screen. At this time, it is quite difficult for a game-player to know the positional relationships between the player character being operated by the game-player and teammates and opponent players who are present around the player character.
Accordingly, a radar image is configured so as to be centered around the player character and to indicate the positional relationships between the player character and the teammates and opponent players, and this radar image is displayed on a monitor different from the main screen.
In military applications, radar display methods are applied to target acquisition techniques using sound. In active sonar, reflected waves of sound, emitted from a warship, propagating through water are received by a receiver of the warship to detect other ships and specify their positions. Since the state of sound propagation varies depending on water flow and temperature, correction is applied to the received data. The sound propagation state is displayed on a display screen of a control device as a radar screen. It should be noted that, in passive sonars, sound waves are not actively emitted from the warship, but rather, sound produced from other ships is received by a sound detector and the positions of the other ships are specified.
[Patent Document 1] Japanese Unexamined Patent Application Publication H10-263205
There are conventional games in which enemy characters arranged within at least a predetermined range in a game space react to a sound effect that is produced in response to an event caused by a player input and the enemy characters, who had been on standby up until that point of time, begin to attack the player character (“Bonanza Bros.,” a commercial game by Sega Corporation in 1990). Since the movements of the enemy characters therein were changed in response to the occurrence of an event itself, it was not actually determined whether or not the sound that had been produced by the actual event had in fact reached the enemy characters (whether or not it was heard by the enemy characters), which has given a game-player a sense of unnaturalness when an event occurred and all the enemies within the predetermined range reacted regardless of their distances from the source of the sound.